Derating of Pump Motors at Higher Altitude
Derating of Pump Motors at Higher Altitude
(OP)
Hello Everbody
I need a suggestion on the installation of pumps at Higher altitude
I need to install a Chilled water pump at an altitude of 2200 Meters above sea Level, The motor i am using is an TEFC AC Induction motor. The motor Manufacturer recomends to derate the mtore if the installation is above 1000 Above sea Level
Since this is all about the avialablilty of air at Higher Altitude and the motors needs to be derated
My question is if i install these pump in an airconditioned space,Do i still need to derate the Motors
If yes then please let me know the reasons and if no the wat is the reason
Thanks in advance for our Sugessions
Vec
I need a suggestion on the installation of pumps at Higher altitude
I need to install a Chilled water pump at an altitude of 2200 Meters above sea Level, The motor i am using is an TEFC AC Induction motor. The motor Manufacturer recomends to derate the mtore if the installation is above 1000 Above sea Level
Since this is all about the avialablilty of air at Higher Altitude and the motors needs to be derated
My question is if i install these pump in an airconditioned space,Do i still need to derate the Motors
If yes then please let me know the reasons and if no the wat is the reason
Thanks in advance for our Sugessions
Vec





RE: Derating of Pump Motors at Higher Altitude
"Standard motors are suitable for operation up to 3300 feet; motors with service factor may be used at altitudes up to 9900 feet at 1.0 service factor."
"Operated at less load (a motor with service factor rating of
1.15 or higher can be operated at altitudes up to 9000 feet with a
1.0 service factor)"
http://www.dreisilker.com/Documents/Ctrl_Hyperlink...
See the linked page:
RE: Derating of Pump Motors at Higher Altitude
The reply is bit confusing me
i was told that at higher altitude the motors does not get enough air for cooling and hence the Out put of motors is reduced, and to get the required power we need to derate the motor
if cooling is the only criteria at higher altitude then can i install these motors in airconditioned room and by doing this i do not derate the motor
can you please help me in answering this is brief
Thank you
RE: Derating of Pump Motors at Higher Altitude
RE: Derating of Pump Motors at Higher Altitude
40°C ambient. For purposes of standardization it is considered that
there is no difference in motor operating temperature between sea
level and 3300 feet altitude.
The cooling effect of ventilating air is a function of its density. The
atmospheric pressure and density at higher altitudes is reduced and
the air cannot remove as much motor heat, causing the motor to run
hotter. As a general guide, motor temperature rise increases 1% for
every 330 feet above 3300 feet. To keep motor heating within safe
limits at altitudes above 3300 feet, there are the following
alternatives:
A. Supply a motor designed for standard sea level operation which
can either be:
(1) Operated at less load (a motor with service factor rating of
1.15 or higher can be operated at altitudes up to 9000 feet with a
1.0 service factor), or
(2) Operated in a lower ambient temperature per the following
table:
If Ambient Max. Altitude with
Temperature is: Same Service Factor is:
30° C 6600 ft.
20° C 9900 ft.
It should be remembered that, although the outdoor ambient tem-
perature at higher altitudes is low, motors probably will be
installed indoors in higher ambient temperatures. Motors applied per A(1) or A(2) above, will have no special altitude or temperature data on the nameplate.
B. Supply a special motor designed for the required high altitude
operation, with appropriate data stamped on the nameplate.
RE: Derating of Pump Motors at Higher Altitude
Cooling is a function of density, as bimers article says, which is a function of absolute pressure and absolute temperature. However a small change in pressure has a much more pronounced effect on air density than does a large change in temperature.
Air density at 10,000 feet is 10.1 psia/14.7 psia = 69% of sea level, a 31% REDUCTION, and that's keeping the same, say 60° F temperature at sea level and at 10,000 ft altitude.
60 F (15.5 C) = 520 R
Now drop the temperature all the way down to 0 F (-18 C) = 460 R
Density is increased at that very low operating temperature by ONLY 460/520 = 13%
SO A NET REDUCTION OF 18%, IF OPERATED AT -18C
Operated inside a heated building, or perhaps simply an unventilated building, (not that many places need AC at 10,000 ft elev), its back to the 31% DECREASE
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
If you have high altitude and at the same time also ambient temp lower that 40C you also can apply the up-rate factor.
see attached page extracted from a Technical Guide book published by a motor manufacturer.
RE: Derating of Pump Motors at Higher Altitude
Service factor is a multiplier that indicates how much a motor can be overloaded. For example, a 10-hp motor with a 1.15 service factor can handle an 11.5-hp load for short periods of time without incurring significant damage. Although many motors have service factors of 1.15, running the motor continuously above rated load reduces efficiency and motor life.
You say that you have a TEFC motor which usually has a 1.15 service factor. If you had a TENV motor, then the service factor is commonly 1.0. So in effect, you have already upgraded the motor by going to a TEFC motor.
The question is, what percentage of rated load will you be operating. If you will be at 85-100% operating continuously, then you should will have to evaluate this further.
RE: Derating of Pump Motors at Higher Altitude
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
Always consult the manufacturer to verify. See this thread http://www.eng-tips.com/viewthread.cfm?qid=24254
Did you do a search before posting? Also, this is a motor de-rate issue ... would have been better in the electrical section
RE: Derating of Pump Motors at Higher Altitude
Again. Service factors are part of the service specification. If you require a service factor, how is it possible to eliminate that requirement by installing it at 2000 m? This "Not necessary to derate a motor with a service factor logic", makes no sense whatsoever.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
When you operate a motor into the service factor load you are actually running the motor much hotter than when you run below the 1.0 SF rating.
Most industrial motors are built with Class F insulation material but operate at class B temp. rise at 1.0 service factory.
You will find the motor maker will state that the 1.10 or 1.15 service factor rating will be operating at Class F temp. rise.
RE: Derating of Pump Motors at Higher Altitude
RE: Derating of Pump Motors at Higher Altitude
I agree. However, there is a NEMA MG1 motor derate chart given to me yrs ago. For the life of me, I cannot find it The closest I came was my link to http://ufgscriteria.tpub.com/ufc_3-520-01/ufc_3-52.... In short, at 2200M, a motor specified with a SF, does NOT require a de-rate
RE: Derating of Pump Motors at Higher Altitude
PumpsOnly,
OK. I can understand that the power output will be the same; it has to be as the pump only draws the power it needs to do its work and the motor supplies that quantity; so no change on the demand side. BUT.. any energy balance suggests that excess heat generated must be subtracted from somewhere, so if excess heat is being generated by the windings and output power is the same, then input power must have been increased in order not to result in a lesser output.
ElCid,
Charts are nice, but don't explain a thing. The increased insulation, from reduced air density, explains how the voltage holds up, but not what's going on with the heat. My understanding, or lack thereof, concerning service factors has always been in relation to how much relative operating time a motor can spend over design load, where excess heat is generated and winding temperatures run hotter than normal. The only resoning that even comes close to explaining why a derate is not made is the possible cooling capacity increase from lower ambient temperatures. I have proven (to my satisfaction) how cooling does not require a rerate, so therefore the SF would also not require a reduction. Now my question is, why was SF mentioned as a condition when discussing the potential rerating of a motor brought to altitude.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
As mentioned above, most motors operate at class B insulation and have class F. The SF "forces" the manufacturer to "add a little more" of the class F insulation into the motor. This allows a motor, with an SF, to operate without derating up to 3000 ft (different than chart I linked to, but I was always told 3000 was the break even point. Probably a rule of thumb). Links to some papers ... and I always default to my electrical or manufacturer to verify operation
http://www.neiengineering.com/wp-content/uploads/2...
In short, altitude beyond 3000 feet above sea level, thinner air negatively impacts the ability of the insulation to adequately cool. Specifying a motor with a SF adds insulation which allows for the derate to start at a higher elevation (~9000 ft or 3000 m). Always consult the manufacturer. This is a synopsis of how it was taught/explained to me.
RE: Derating of Pump Motors at Higher Altitude
PumpsOnly, Table II of that reference suggests that the temperature is allowed to decrease from 40 to 20 C when moving to 3000 m altitude, suggesting that ambient temp is correlated to output, not winding temperature. That temperature reduction I believe tends to confirm my analysis above, as I assumed close to the same 20 C at altitude.
While my simple air density and temperature does not consider SF, or indicates that it would not require a reduction from 1.15 to 1, the above link does. I suspect that the reduction in SF is necessary due to a tendency of an overloaded motor to generate even more heat than usual, which won't be as easily disipated at altitude.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Derating of Pump Motors at Higher Altitude
In your statement above, you left off "at an ambient temperature of 40 C".
It may be semantics, I don't believe that operating at a reduced temperature is considered to be a derate on the motor. It is a limit on the design operating conditions. See the attachment.
"A motor with a higher insulation class may not require derating in these conditions."
http://www.wermac.com/acm_2.pdf
In addition, "It should be noted that any motor operating continuously at a service factor greater than 1 will have a reduced life expectancy compared to operating it at it’s rated horsepower."
http://www.wermac.com/acm_2.pdf
jraef (Electrical) posted this comment on service factor:
"Service Factor (SF) is a concept uniquie to NEMA design motors and is defined as a percentage by which the motor can withstand an increased load while still maintaining rated torque and speed within an accepted tolerance, even though current is expected to rise. Some believe this to be a short time rating, however you will never find an AMOUNT of time discussed, mostly because it is nebulous. What is said is that when using a motor's SF, an increased temperature rise is to be expected and therefore the motor life will not be the same as if the SF was not used. Many OEMs choose to use SF as if it represented an increased HP at the shaft, mostly in order to avoid stepping up to the next size motor if their application calls for just a little more than a standard motor design allows. Those OEMs are generally not concerned that the motor will last 5 years instead of 20 years, because either way it is out of their warranty by the time it fails."
http://www.eng-tips.com/viewthread.cfm?qid=161272
RE: Derating of Pump Motors at Higher Altitude
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek